Speaker Amplifier Feedback Circuit for Flat Impedance Drive
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Solution Overview
Problem
Existing power amplifying devices fail to achieve a flat frequency characteristic for the input voltage of a speaker, leading to non-flat frequency characteristics of the emitted sound, and result in current magnetostriction issues.
Innovation Solution
A power amplifying device with a voltage feedback circuit and a current feedback circuit that includes a voltage feedback resistor and a compensation circuit in parallel with the acoustic transducer, generating a flat parallel impedance and an output resistor greater than the acoustic transducer's resistance, virtually connected in series, to reduce current magnetostriction and flatten the frequency characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a circuit is connected in series with the speaker to improve current magnetostriction, then current magnetostriction is reduced, but the frequency characteristic of the input voltage becomes non-flat
Solution Approach 1:
The patent employs a feedback circuit that detects the voltage across the speaker and feeds it back to the amplifier output terminal. This feedback mechanism allows the system to compensate for the impedance variations of the speaker, maintaining a flat frequency characteristic while still benefiting from the series circuit's current magnetostriction reduction effect.
Solution Approach 2:
The patent changes the electrical parameters by introducing a feedback circuit that dynamically adjusts the voltage based on the speaker's impedance characteristics. This parameter adjustment allows the system to overcome the non-flat frequency response caused by the series circuit connection.
2Object-generated harmful factors
If the speaker is driven with low impedance at low-frequency resonance to improve current magnetostriction, then current magnetostriction improves, but the overall frequency characteristic becomes non-flat
Solution Approach 1:
The feedback circuit continuously monitors the voltage across the speaker and provides corrective feedback to the amplifier. This allows the system to compensate for the impedance peaks at low-frequency resonance, maintaining a flat frequency response while allowing the series circuit to reduce current magnetostriction.
Solution Approach 2:
The feedback circuit is designed to anticipate and counteract the impedance variations that occur at low-frequency resonance. By providing preliminary correction through feedback, the system prevents the frequency characteristic from becoming non-flat while still achieving current magnetostriction reduction.
3Object-generated harmful factors
If a series circuit is added to reduce current magnetostriction, then current magnetostriction is reduced, but the device complexity increases
Solution Approach 1:
The feedback circuit serves multiple functions: it compensates for speaker impedance variations to maintain flat frequency response, and it enables the series circuit to effectively reduce current magnetostriction. This multi-functionality justifies the added complexity by delivering multiple benefits from a single circuit addition.
Solution Approach 2:
The feedback circuit acts as an intermediary between the speaker and the amplifier, mediating the interaction to achieve both flat frequency response and current magnetostriction reduction. This intermediary role allows the series circuit to function effectively without directly causing frequency response issues.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively drives the acoustic transducer with a flat frequency characteristic while reducing current magnetostriction, achieving improved sound quality by compensating for motional impedance and minimizing power loss.
Implementation Method 1
a voltage feedback circuit configured to negatively feed back a voltage of the output sound signal to an input of the amplifier circuit; and a current feedback circuit configured to negatively feed back a current flowing through the acoustic transducer to the input of the amplifier circuit
Implementation Method 2
an acoustic transducer configured to convert the output sound signal into sound
Data Source
AI summary
A power amplifying device includes: an amplifier circuit configured to amplify an input sound signal and output an output sound signal to an acoustic transducer; and a current feedback circuit configured to negatively feed back a current flowing through the acoustic transducer to the amplifier circuit. The voltage feedback circuit includes a voltage feedback resistor and a compensation circuit connected in parallel. A compensation impedance connected in parallel with the acoustic transducer and an output resistor connected in series with the acoustic transducer are virtually generated by the voltage feedback circuit and the current feedback circuit. An impedance of a parallel circuit of the acoustic transducer and the compensation impedance is flat as compared with a frequency characteristic of an impedance of the acoustic transducer. The output resistor has a value greater than a resistance value of the acoustic transducer.